Partial Failure of a Bulk Storage Facility: Construction Defect vs. Design Error

摘要

Engineers are sometimes tasked with designs involving loading conditions atypical to those encountered in their common practice. In some cases, the materials imparting loads on the constructed facility behave incongruously with design assumptions. It is incumbent upon the designer to thoroughly evaluate the characteristics of materials imparting loads upon the designed structure so the constructed facility can adequately sustain service conditions. For example, a bulk fertilizer operation in North Carolina contracted a local engineer to design a covered containment structure to stockpile fertilizer products. A general contractor erected the 2,360 m2 (25,400 ft2) structure, including concrete perimeter and partition walls, wood-framed perimeter walls, partition walls, interior columns, and roof structure; and steel tie rods, with intermediate wood and LVL support beams. Days after first loading bulk material by overhead conveyor into the largest of the six interior bins, the owner observed numerous broken tie rods and, upon emptying the bin, found many wood and LVL tie rod supports fractured and unseated. This paper presents the findings of a limited engineering investigation into the cause of the observed failures, including various analysis methods and evaluation of failure modes posed by the owner's representative. Despite construction defects identified during the investigation, analyses revealed errant framing design and/or loading assumptions as the proximate cause(s) of failure.